At least in all modern versions of OpenSSL, it is enough to call
SSL_renegotiate() once, and then forget about it. Subsequent SSL_write()
and SSL_read() calls will finish the handshake.
The SSL_set_session_id_context() call is unnecessary too. We only have
one SSL context, and the SSL session was created with that to begin with.
This omission leaked one PGresult per WAL streaming cycle, which possibly
would never be enough to notice in the real world, but it's still a leak.
Per Coverity. Back-patch to 9.3 where the error was introduced.
We'd leak the ident_serv data structure if the second pg_getaddrinfo_all
(the one for the local address) failed. This is not of great consequence
because a failure return here just leads directly to backend exit(), but
if this function is going to try to clean up after itself at all, it should
not have such holes in the logic. Try to fix it in a future-proof way by
having all the failure exits go through the same cleanup path, rather than
"optimizing" some of them.
Per Coverity. Back-patch to 9.2, which is as far back as this patch
applies cleanly.
Back in commit 400e2c9344 I rewrote GEQO's
gimme_tree function to improve its heuristic for modifying the given tour
into a legal join order. In what can only be called a fit of hubris,
I supposed that this new heuristic would *always* find a legal join order,
and ripped out the old logic that allowed gimme_tree to sometimes fail.
The folly of this is exposed by bug #12760, in which the "greedy" clumping
behavior of merge_clump() can lead it into a dead end which could only be
recovered from by un-clumping. We have no code for that and wouldn't know
exactly what to do with it if we did. Rather than try to improve the
heuristic rules still further, let's just recognize that it *is* a
heuristic and probably must always have failure cases. So, put back the
code removed in the previous commit to allow for failure (but comment it
a bit better this time).
It's possible that this code was actually fully correct at the time and
has only been broken by the introduction of LATERAL. But having seen this
example I no longer have much faith in that proposition, so back-patch to
all supported branches.
Fix some issues I noticed while fooling with an extension to allow an
additional kind of toast pointer. Much of this is just comment
improvement, but there are a couple of actual bugs, which might or might
not be reachable today depending on what can happen during logical
decoding. An example is that toast_flatten_tuple() failed to cover the
possibility of an indirection pointer in its input. Back-patch to 9.4
just in case that is reachable now.
In HEAD, also correct some really minor issues with recent compression
reorganization, such as dangerously underparenthesized macros.
To get CRC functionality in a client program, you now need to link with
libpgcommon instead of libpgport. The CRC code has nothing to do with
portability, so libpgcommon is a better home. (libpgcommon didn't exist
when pg_crc.c was originally moved to src/port.)
Remove the possibility to get CRC functionality by just #including
pg_crc_tables.h. I'm not aware of any extensions that actually did that and
couldn't simply link with libpgcommon.
This also moves the pg_crc.h header file from src/include/utils to
src/include/common, which will require changes to any external programs
that currently does #include "utils/pg_crc.h". That seems acceptable, as
include/common is clearly the right home for it now, and the change needed
to any such programs is trivial.
The meta data of PGLZ symbolized by PGLZ_Header is removed, to make
the compression and decompression code independent on the backend-only
varlena facility. PGLZ_Header is being used to store some meta data
related to the data being compressed like the raw length of the uncompressed
record or some varlena-related data, making it unpluggable once PGLZ is
stored in src/common as it contains some backend-only code paths with
the management of varlena structures. The APIs of PGLZ are reworked
at the same time to do only compression and decompression of buffers
without the meta-data layer, simplifying its use for a more general usage.
On-disk format is preserved as well, so there is no incompatibility with
previous major versions of PostgreSQL for TOAST entries.
Exposing compression and decompression APIs of pglz makes possible its
use by extensions and contrib modules. Especially this commit is required
for upcoming WAL compression feature so that the WAL reader facility can
decompress the WAL data by using pglz_decompress.
Michael Paquier, reviewed by me.
We reserve space for the full amount, not one less. The affected checks
deal with localized month and day names. Today's DCH_MAX_ITEM_SIZ value
would suffice for a 60-byte day name, while the longest known is the
49-byte mn_CN.utf-8 word for "Saturday." Thus, the upshot of this
change is merely to avoid misdirecting future readers of the code; users
are not expected to see errors either way.
When beginning streaming replication, the client usually issues the
IDENTIFY_SYSTEM command, which used to return the current WAL insert
position. That's not suitable for the intended purpose of that field,
however. pg_receivexlog uses it to start replication from the reported
point, but if it hasn't been flushed to disk yet, it will fail. Change
IDENTIFY_SYSTEM to report the flush position instead.
Backpatch to 9.1 and above. 9.0 doesn't report any WAL position.
It was getting tedious to track and release all the different things that
form a scan key. We were leaking at least the queryCategories array, and
possibly more, on a rescan. That was visible if a GIN index was used in a
nested loop join. This also protects from leaks in extractQuery method.
No backpatching, given the lack of complaints from the field. Maybe later,
after this has received more field testing.
If an insertion or update had to wait for another transaction to finish,
because there was another insertion with conflicting key in progress,
we would pass a just-free'd item pointer to XactLockTableWait().
All calls to XactLockTableWait() and MultiXactIdWait() had similar issues.
Some passed a pointer to a buffer in the buffer cache, after already
releasing the lock. The call in EvalPlanQualFetch had already released the
pin too. All but the call in execUtils.c would merely lead to reporting a
bogus ctid, however (or an assertion failure, if enabled).
All the callers that passed HeapTuple->t_data->t_ctid were slightly bogus
anyway: if the tuple was updated (again) in the same transaction, its ctid
field would point to the next tuple in the chain, not the tuple itself.
Backpatch to 9.4, where the 'ctid' argument to XactLockTableWait was added
(in commit f88d4cfc)
It's perfectly fine to have blocked interrupts when
ProcessClientWriteInterrupt() is called. In fact it's commonly the
case when emitting error reports. And we deal with that correctly.
Even if that'd not be the case, it'd be a bad location for such a
assertion. Because ProcessClientWriteInterrupt() is only called when
the socket is blocked it's hard to hit.
Per Heikki and buildfarm animals nightjar and dunlin.
The remaining caller (lwlocks) doesn't need that facility, and we plan
to remove ImmedidateInterruptOK entirely. That means that interrupts
can't be serviced race-free and portably anyway, so there's little
reason for keeping the feature.
Reviewed-By: Heikki Linnakangas
Deadlock checking was performed inside signal handlers up to
now. While it's a remarkable feat to have made this work reliably,
it's quite complex to understand why that is the case. Partially it
worked due to the assumption that semaphores are signal safe - which
is not actually documented to be the case for sysv semaphores.
The reason we had to rely on performing this work inside signal
handlers is that semaphores aren't guaranteed to be interruptable by
signals on all platforms. But now that latches provide a somewhat
similar API, which actually has the guarantee of being interruptible,
we can avoid doing so.
Signalling between ProcSleep, ProcWakeup, ProcWaitForSignal and
ProcSendSignal is now done using latches. This increases the
likelihood of spurious wakeups. As spurious wakeup already were
possible and aren't likely to be frequent enough to be an actual
problem, this seems acceptable.
This change would allow for further simplification of the deadlock
checking, now that it doesn't have to run in a signal handler. But
even if I were motivated to do so right now, it would still be better
to do that separately. Such a cleanup shouldn't have to be reviewed a
the same time as the more fundamental changes in this commit.
There is one possible usability regression due to this commit. Namely
it is more likely than before that log_lock_waits messages are output
more than once.
Reviewed-By: Heikki Linnakangas
We used to handle authentication_timeout by setting
ImmediateInterruptOK to true during large parts of the authentication
phase of a new connection. While that happens to work acceptably in
practice, it's not particularly nice and has ugly corner cases.
Previous commits converted the FE/BE communication to use latches and
implemented support for interrupt handling during both
send/recv. Building on top of that work we can get rid of
ImmediateInterruptOK during authentication, by immediately treating
timeouts during authentication as a reason to die. As die interrupts
are handled immediately during client communication that provides a
sensibly quick reaction time to authentication timeout.
Additionally add a few CHECK_FOR_INTERRUPTS() to some more complex
authentication methods. More could be added, but this already should
provides a reasonable coverage.
While it this overall increases the maximum time till a timeout is
reacted to, it greatly reduces complexity and increases
reliability. That seems like a overall win. If the increase proves to
be noticeable we can deal with those cases by moving to nonblocking
network code and add interrupt checking there.
Reviewed-By: Heikki Linnakangas
This field has been unreferenced since 1998, and does not appear in lseg
values stored on disk (since sizeof(lseg) is only 32 bytes according to
pg_type). There was apparently some idea of maintaining it just in values
appearing in memory, but the bookkeeping required to make that work would
surely far outweigh the cost of recalculating the line's slope when needed.
Remove it to (a) simplify matters and (b) suppress some uninitialized-field
whining from Coverity.
Up to now it was impossible to terminate a backend that was trying to
send/recv data to/from the client when the socket's buffer was already
full/empty. While the send/recv calls itself might have gotten
interrupted by signals on some platforms, we just immediately retried.
That could lead to situations where a backend couldn't be terminated ,
after a client died without the connection being closed, because it
was blocked in send/recv.
The problem was far more likely to be hit when sending data than when
reading. That's because while reading a command from the client, and
during authentication, we processed interrupts immediately . That
primarily left COPY FROM STDIN as being problematic for recv.
Change things so that that we process 'die' events immediately when
the appropriate signal arrives. We can't sensibly react to query
cancels at that point, because we might loose sync with the client as
we could be in the middle of writing a message.
We don't interrupt writes if the write buffer isn't full, as indicated
by write() returning EWOULDBLOCK, as that would lead to fewer error
messages reaching clients.
Per discussion with Kyotaro HORIGUCHI and Heikki Linnakangas
Discussion: 20140927191243.GD5423@alap3.anarazel.de
Up to now large swathes of backend code ran inside signal handlers
while reading commands from the client, to allow for speedy reaction to
asynchronous events. Most prominently shared invalidation and NOTIFY
handling. That means that complex code like the starting/stopping of
transactions is run in signal handlers... The required code was
fragile and verbose, and is likely to contain bugs.
That approach also severely limited what could be done while
communicating with the client. As the read might be from within
openssl it wasn't safely possible to trigger an error, e.g. to cancel
a backend in idle-in-transaction state. We did that in some cases,
namely fatal errors, nonetheless.
Now that FE/BE communication in the backend employs non-blocking
sockets and latches to block, we can quite simply interrupt reads from
signal handlers by setting the latch. That allows us to signal an
interrupted read, which is supposed to be retried after returning from
within the ssl library.
As signal handlers now only need to set the latch to guarantee timely
interrupt processing, remove a fair amount of complicated & fragile
code from async.c and sinval.c.
We could now actually start to process some kinds of interrupts, like
sinval ones, more often that before, but that seems better done
separately.
This work will hopefully allow to handle cases like being blocked by
sending data, interrupting idle transactions and similar to be
implemented without too much effort. In addition to allowing getting
rid of ImmediateInterruptOK, that is.
Author: Andres Freund
Reviewed-By: Heikki Linnakangas
This allows to introduce more elaborate handling of interrupts while
reading from a socket. Currently some interrupt handlers have to do
significant work from inside signal handlers, and it's very hard to
correctly write code to do so. Generic signal handler limitations,
combined with the fact that we can't safely jump out of a signal
handler while reading from the client have prohibited implementation
of features like timeouts for idle-in-transaction.
Additionally we use the latch code to wait in a couple places where we
previously only had waiting code on windows as other platforms just
busy looped.
This can increase the number of systemcalls happening during FE/BE
communication. Benchmarks so far indicate that the impact isn't very
high, and there's room for optimization in the latch code. The chance
of cleaning up the usage of latches gives us, seem to outweigh the
risk of small performance regressions.
This commit theoretically can't used without the next patch in the
series, as WaitLatchOrSocket is not defined to be fully signal
safe. As we already do that in some cases though, it seems better to
keep the commits separate, so they're easier to understand.
Author: Andres Freund
Reviewed-By: Heikki Linnakangas
LINE doesn't have an "m" field (anymore anyway). Also fix unportable
assumption that %x can print the result of pointer subtraction.
In passing, improve single_decode() in minor ways:
* Remove unnecessary leading-whitespace skip (strtod does that already).
* Make GEODEBUG message more intelligible.
* Remove entirely-useless test to see if strtod returned a silly pointer.
* Don't bother computing trailing-whitespace skip unless caller wants
an ending pointer.
This has been broken since 261c7d4b65.
Although it's only debug code, might as well fix the 9.4 branch too.
The logic to compact away removed tuples from page was duplicated with
small differences in PageRepairFragmentation, PageIndexMultiDelete, and
PageIndexDeleteNoCompact. Put it into a common function.
Reviewed by Peter Geoghegan.
Sometimes it's useful for a background worker to be able to initialize
its database connection by OID rather than by name, so provide a way
to do that.
If any error occurred while we were in the middle of reading a protocol
message from the client, we could lose sync, and incorrectly try to
interpret a part of another message as a new protocol message. That will
usually lead to an "invalid frontend message" error that terminates the
connection. However, this is a security issue because an attacker might
be able to deliberately cause an error, inject a Query message in what's
supposed to be just user data, and have the server execute it.
We were quite careful to not have CHECK_FOR_INTERRUPTS() calls or other
operations that could ereport(ERROR) in the middle of processing a message,
but a query cancel interrupt or statement timeout could nevertheless cause
it to happen. Also, the V2 fastpath and COPY handling were not so careful.
It's very difficult to recover in the V2 COPY protocol, so we will just
terminate the connection on error. In practice, that's what happened
previously anyway, as we lost protocol sync.
To fix, add a new variable in pqcomm.c, PqCommReadingMsg, that is set
whenever we're in the middle of reading a message. When it's set, we cannot
safely ERROR out and continue running, because we might've read only part
of a message. PqCommReadingMsg acts somewhat similarly to critical sections
in that if an error occurs while it's set, the error handler will force the
connection to be terminated, as if the error was FATAL. It's not
implemented by promoting ERROR to FATAL in elog.c, like ERROR is promoted
to PANIC in critical sections, because we want to be able to use
PG_TRY/CATCH to recover and regain protocol sync. pq_getmessage() takes
advantage of that to prevent an OOM error from terminating the connection.
To prevent unnecessary connection terminations, add a holdoff mechanism
similar to HOLD/RESUME_INTERRUPTS() that can be used hold off query cancel
interrupts, but still allow die interrupts. The rules on which interrupts
are processed when are now a bit more complicated, so refactor
ProcessInterrupts() and the calls to it in signal handlers so that the
signal handlers always call it if ImmediateInterruptOK is set, and
ProcessInterrupts() can decide to not do anything if the other conditions
are not met.
Reported by Emil Lenngren. Patch reviewed by Noah Misch and Andres Freund.
Backpatch to all supported versions.
Security: CVE-2015-0244
Previously very long localized month and weekday strings could
overflow the allocated buffers, causing a server crash.
Reported and patch reviewed by Noah Misch. Backpatch to all
supported versions.
Security: CVE-2015-0241
Previously very long field masks for floats could access memory
beyond the existing buffer allocated to hold the result.
Reported by Andres Freund and Peter Geoghegan. Backpatch to all
supported versions.
Security: CVE-2015-0241
We've been trying to support \u0000 in JSON values since commit
78ed8e03c6, and have introduced increasingly worse hacks to try to
make it work, such as commit 0ad1a81632. However, it fundamentally
can't work in the way envisioned, because the stored representation looks
the same as for \\u0000 which is not the same thing at all. It's also
entirely bogus to output \u0000 when de-escaped output is called for.
The right way to do this would be to store an actual 0x00 byte, and then
throw error only if asked to produce de-escaped textual output. However,
getting to that point seems likely to take considerable work and may well
never be practical in the 9.4.x series.
To preserve our options for better behavior while getting rid of the nasty
side-effects of 0ad1a81632, revert that commit in toto and instead
throw error if \u0000 is used in a context where it needs to be de-escaped.
(These are the same contexts where non-ASCII Unicode escapes throw error
if the database encoding isn't UTF8, so this behavior is by no means
without precedent.)
In passing, make both the \u0000 case and the non-ASCII Unicode case report
ERRCODE_UNTRANSLATABLE_CHARACTER / "unsupported Unicode escape sequence"
rather than claiming there's something wrong with the input syntax.
Back-patch to 9.4, where we have to do something because 0ad1a81632
broke things for many cases having nothing to do with \u0000. 9.3 also has
bogus behavior, but only for that specific escape value, so given the lack
of field complaints it seems better to leave 9.3 alone.
Using the new interface MemoryContextAllocExtended, callers can
specify MCXT_ALLOC_NO_OOM if they are prepared to handle a NULL
return value.
Michael Paquier, reviewed and somewhat revised by me.
calc_rangesel() failed outright when comparing range variables to empty
constant ranges with < or >=, as a result of missing cases in a switch.
It also produced a bogus estimate for > comparison to an empty range.
On top of that, the >= and > cases were mislabeled throughout. For
nonempty constant ranges, they managed to produce the right answers
anyway as a result of counterbalancing typos.
Also, default_range_selectivity() omitted cases for elem <@ range,
range &< range, and range &> range, so that rather dubious defaults
were applied for these operators.
In passing, rearrange the code in rangesel() so that the elem <@ range
case is handled in a less opaque fashion.
Report and patch by Emre Hasegeli, some additional work by me
The requiredEntries / additionalEntries arrays were not freed in
freeScanKeys() like other per-key stuff.
It's not obvious, but startScanKey() was only ever called after the keys
have been initialized with ginNewScanKey(). That's why it doesn't need to
worry about freeing existing arrays. The ginIsNewKey() test in gingetbitmap
was never true, because ginrescan free's the existing keys, and it's not OK
to call gingetbitmap twice in a row without calling ginrescan in between.
To make that clear, remove the unnecessary ginIsNewKey(). And just to be
extra sure that nothing funny happens if there is an existing key after all,
call freeScanKeys() to free it if it exists. This makes the code more
straightforward.
(I'm seeing other similar leaks in testing a query that rescans an GIN index
scan, but that's a different issue. This just fixes the obvious leak with
those two arrays.)
Backpatch to 9.4, where GIN fast scan was added.
In 804b6b6db4 we modified
BuildIndexValueDescription to pay attention to which columns are visible
to the user, but unfortunatley that commit neglected to consider indexes
which are built on expressions.
Handle error-reporting of violations of constraint indexes based on
expressions by not returning any detail when the user does not have
table-level SELECT rights.
Backpatch to 9.0, as the prior commit was.
Pointed out by Tom.
GetLockConflicts() has for a long time not properly terminated the
returned array. During normal processing the returned array is zero
initialized which, while not pretty, is sufficient to be recognized as
a invalid virtual transaction id. But the HotStandby case is more than
aesthetically broken: The allocated (and reused) array is neither
zeroed upon allocation, nor reinitialized, nor terminated.
Not having a terminating element means that the end of the array will
not be recognized and that recovery conflict handling will thus read
ahead into adjacent memory. Only terminating when hitting memory
content that looks like a invalid virtual transaction id. Luckily
this seems so far not have caused significant problems, besides making
recovery conflict more expensive.
Discussion: 20150127142713.GD29457@awork2.anarazel.de
Backpatch into all supported branches.
Benchmarks has shown that aligning the buffer descriptor array to
cache lines is important for scalability; especially on bigger,
multi-socket, machines.
Currently the array sometimes already happens to be aligned by
happenstance, depending how large previous shared memory allocations
were. That can lead to wildly varying performance results after minor
configuration changes.
In addition to aligning the start of descriptor array, also force the
size of individual descriptors to be of a common cache line size (64
bytes). That happens to already be the case on 64bit platforms, but
this way we can change the struct BufferDesc more easily.
As the alignment primarily matters in highly concurrent workloads
which probably all are 64bit these days, and the space wastage of
element alignment would be a bit more noticeable on 32bit systems, we
don't force the stride to be cacheline sized on 32bit platforms for
now. If somebody does actual performance testing, we can reevaluate
that decision by changing the definition of BUFFERDESC_PADDED_SIZE.
Discussion: 20140202151319.GD32123@awork2.anarazel.de
Per discussion with Bruce Momjan, Tom Lane, Robert Haas, and Peter
Geoghegan.
When gin_fuzzy_search_limit was used, we could jump out of startScan()
without calling startScanKey(). That was harmless in 9.3 and below, because
startScanKey()() didn't do anything interesting, but in 9.4 it initializes
information needed for skipping entries (aka GIN fast scans), and you
readily get a segfault if it's not done. Nevertheless, it was clearly wrong
all along, so backpatch all the way to 9.1 where the early return was
introduced.
(AFAICS startScanKey() did nothing useful in 9.3 and below, because the
fields it initialized were already initialized in ginFillScanKey(), but I
don't dare to change that in a minor release. ginFillScanKey() is always
called in gingetbitmap() even though there's a check there to see if the
scan keys have already been initialized, because they never are; ginrescan()
free's them.)
In the passing, remove unnecessary if-check from the second inner loop in
startScan(). We already check in the first loop that the condition is true
for all entries.
Reported by Olaf Gawenda, bug #12694, Backpatch to 9.1 and above, although
AFAICS it causes a live bug only in 9.4.
This potentially allows us to add mcxt.c interfaces that do something
other than throw an error when memory cannot be allocated. We'll
handle adding those interfaces in a separate commit.
Michael Paquier, with minor changes by me
The row level security patches didn't add the 'usebypassrls' columns to
the pg_user and pg_shadow views on the belief that they were deprecated,
but we havn't actually said they are and therefore we should include it.
This patch corrects that, adds missing documentation for rolbypassrls
into the system catalog page for pg_authid, along with the entries for
pg_user and pg_shadow, and cleans up a few other uses of 'row-level'
cases to be 'row level' in the docs.
Pointed out by Amit Kapila.
Catalog version bump due to system view changes.
Commit 804b6b6db4 added the build of a
range table in copy.c to initialize the EState es_range_table since it
can be needed in error paths. Unfortunately, that commit didn't
appreciate that some code paths might end up not initializing the rte
which is used to build the range table.
Fix that and clean up a couple others things along the way- build it
only once and don't explicitly set it on the !is_from path as it
doesn't make any sense there (cstate is palloc0'd, so this isn't an
issue from an initializing standpoint either).
The prior commit went back to 9.0, but this only goes back to 9.1 as
prior to that the range table build happens immediately after building
the RTE and therefore doesn't suffer from this issue.
Pointed out by Robert.
While building error messages to return to the user,
BuildIndexValueDescription, ExecBuildSlotValueDescription and
ri_ReportViolation would happily include the entire key or entire row in
the result returned to the user, even if the user didn't have access to
view all of the columns being included.
Instead, include only those columns which the user is providing or which
the user has select rights on. If the user does not have any rights
to view the table or any of the columns involved then no detail is
provided and a NULL value is returned from BuildIndexValueDescription
and ExecBuildSlotValueDescription. Note that, for key cases, the user
must have access to all of the columns for the key to be shown; a
partial key will not be returned.
Further, in master only, do not return any data for cases where row
security is enabled on the relation and row security should be applied
for the user. This required a bit of refactoring and moving of things
around related to RLS- note the addition of utils/misc/rls.c.
Back-patch all the way, as column-level privileges are now in all
supported versions.
This has been assigned CVE-2014-8161, but since the issue and the patch
have already been publicized on pgsql-hackers, there's no point in trying
to hide this commit.
gist_poly_compress() and gist_circle_compress() checked for a NULL-pointer
key argument, but that was dead code; the gist code never passes a
NULL-pointer to the "compress" method.
This commit also removes a documentation note added in commit a0a3883,
about doing NULL-pointer checks in the "compress" method. It was added
based on the fact that some implementations were doing NULL-pointer
checks, but those checks were unnecessary in the first place.
The NULL-pointer check in gbt_var_same() function was also unnecessary.
The arguments to the "same" method come from the "compress", "union", or
"picksplit" methods, but none of them return a NULL pointer.
None of this is to be confused with SQL NULL values. Those are dealt with
by the gist machinery, and are never passed to the GiST opclass methods.
Michael Paquier
Commit 145343534c arranged to store numeric
NaN values as short-header numerics, but the field access macros did not
get the memo: they thought only "SHORT" numerics have short headers.
Most of the time this makes no difference because we don't access the
weight or dscale of a NaN; but numeric_send does that. As pointed out
by Andrew Gierth, this led to fetching uninitialized bytes.
AFAICS this could not have any worse consequences than that; in particular,
an unaligned stored numeric would have been detoasted by PG_GETARG_NUMERIC,
so that there's no risk of a fetch off the end of memory. Still, the code
is wrong on its own terms, and it's not hard to foresee future changes that
might expose us to real risks. So back-patch to all affected branches.
Commit 1be4eb1b2d disabled this, but I
think the real problem here was fixed by commit
b181a91981 and commit
d060e07fa9. So let's try re-enabling
it now and see what happens.
The "pos" variable is modified within PG_TRY and then referenced
within PG_CATCH, so for strict POSIX conformance it must be marked
volatile. Superficially the code looked safe because pos's address
was taken, which was sufficient to force it into memory ... but it's
not sufficient to ensure that the compiler applies updates exactly
where the program text says to. The volatility marking has to extend
into a couple of subroutines too, but I think that's probably a good
thing because the risk of out-of-order updates is mostly in those
subroutines not asyncQueueReadAllNotifications() itself. In principle
the compiler could have re-ordered operations such that an error could
be thrown while "pos" had an incorrect value.
It's unclear how real the risk is here, but for safety back-patch
to all active branches.
On closer inspection, we can remove the "volatile" qualifier on
"using_subtxn" so long as we initialize that before the PG_TRY block,
which there's no particularly good reason not to do.
Also, push the "change" variable inside the PG_TRY so as to remove
all question of whether it needs "volatile", and remove useless
early initializations of "snapshow_now" and "using_subtxn".
Fix unsafe use of a non-volatile variable in PG_TRY/PG_CATCH in
AlterSystemSetConfigFile(). While at it, clean up a bundle of other
infelicities and outright bugs, including corner-case-incorrect linked list
manipulation, a poorly designed and worse documented parse-and-validate
function (which even included some randomly chosen hard-wired substitutes
for the specified elevel in one code path ... wtf?), direct use of open()
instead of fd.c's facilities, inadequate checking of write()'s return
value, and generally poorly written commentary.
Fix unsafe coding around PG_TRY in RelationBuildRowSecurity: can't change
a variable inside PG_TRY and then use it in PG_CATCH without marking it
"volatile". In this case though it seems saner to avoid that by doing
a single assignment before entering the TRY block.
I started out just intending to fix that, but the more I looked at the
row-security code the more distressed I got. This patch also fixes
incorrect construction of the RowSecurityPolicy cache entries (there was
not sufficient care taken to copy pass-by-ref data into the cache memory
context) and a whole bunch of sloppiness around the definition and use of
pg_policy.polcmd. You can't use nulls in that column because initdb will
mark it NOT NULL --- and I see no particular reason why a null entry would
be a good idea anyway, so changing initdb's behavior is not the right
answer. The internal value of '\0' wouldn't be suitable in a "char" column
either, so after a bit of thought I settled on using '*' to represent ALL.
Chasing those changes down also revealed that somebody wasn't paying
attention to what the underlying values of ACL_UPDATE_CHR etc really were,
and there was a great deal of lackadaiscalness in the catalogs.sgml
documentation for pg_policy and pg_policies too.
This doesn't pretend to be a complete code review for the row-security
stuff, it just fixes the things that were in my face while dealing with
the bugs in RelationBuildRowSecurity.
Heikki Linnakangas
Tom Lane
Fujii Masao
Noah Misch
Andres Freund
Robert Haas
Bruce Momjian
Peter Eisentraut
Stephen Frost